1. Field of the Invention
The present invention relates generally to an electronic locking system having a transmitter for emitting a transmission signal and a receiver for receiving the transmitted signal and comparing the received signal to a reference signal for opening the lock upon the identity of the received signal and reference signal. The invention also relates to a method for resynchronization of the transmitter and receiver of such system.
2. Description of the Related Art
In an electronic locking system having a transmitter and receiver, initialization of the system forms the basis for its operation wherein a sequence of reference marks is rigidly prescribed in a reference generator of the receiver, and a sequence of transmission marks identical to the reference marks is rigidly prescribed in a mark generator of the transmitter. After initialization, the reference generator is set to a reference mark which is identical to the transmission mark of the mark generator of the transmitter. The two sequences are thereby identified by a stored algorithm and by starting parameters which are defined by a random process.
In a transmission event, the transmitter emits a transmission signal having one of the transmission marks. For example, the transmission signal may be emitted by a light emitting diode in the infrared range. The transmission signal is converted into an electrical signal in the receiver and the receiver recovers the transmission mark from the transmission signal and compares the transmission mark in the receiver to a reference mark supplied by the reference generator. When the reference mark and the transmission mark are found to be identical and there is synchronization between the transmitter and the receiver, a control means in the receiver initiates opening of the lock. When the reference mark and the transmission mark are found not to be identical, a synchronization unit in the receiver restores synchronization between the reference generator and the mark generator under certain conditions.
A lack of identity between the reference mark and the transmission mark can, for example, occur when the transmitter outputs a transmission signal which does not reach the receiver so that the respective sequences no longer coincide. In this case, re-synchronization of the reference generator in the receiver must be undertaken to get the locking system to open the lock. Of course, lack of identity also occurs during unauthorized attempts to open the lock.
A known locking system is disclosed in European patent application No. 84 10 61 42.7, in which additional information is provided in the transmission signal for re-synchronization. The receiver derives a reference mark from the additional information to which the reference generator in the receiver should be resynchronized by the synchronization unit. The generation and evaluation of the auxiliary information requires additional equipment outlay without providing higher security.